A super-trim Manu Vatuvei was handing the mental advantage to Olympic champion rower Eric Murray as they weighed in for the Fight For Life boxing extravaganza in Auckland today.

That will be the only advantage Vatuvei needs to concede though as he looked in significantly better shape than his opponent.

Vatuvei will take a significant weight edge into the ring, too. He tipped the scales at 104.35kg with Murray logging 100.4kg, putting them well into the heavyweight class.

Vatuvei looked ripped, having lost around 6kg from his playing weight with the Warriors.

"Boxing and Warriors training have helped me shed the kilos," Vatuvei said. "When the season comes, I'll put it back on.

"I'm really looking forward to this. Eric is a tough bloke and he's also mentally tough."

Murray admitted to some nerves and fear but said it was all about channelling that.

"There's always an element of fear in anything you do. But you have to put your faith in your trainers."

Many are tipping the Hika Elliot vs Paul Gallen fight to be the best of the night. All Blacks hooker weighed in at 113.kg, almost 9kg heavier than Gallen, widely regarded as the toughest player in the NRL.

While the Fight For Life will benefit prostate cancer on the evening, there have been some personal touches with Kiwi great Jarrod McCracken handing over a cheque for $38,000 from personal fundraising on either side of the Tasman.

McCracken weighed in almost 10kg heavier than his opponent, former All Black Carlos Spencer who is returning for his second appearance in as many years.

Big Willie Mason lived up to his name, being the heaviest fighter on the card at 121.1kg.

On the professional side of the promotion, transTasman women rivals Lauren Eagle (Australia 59.9kg) and Daniella Smith (New Zealand 59.8kg), looked in great shape.